JP3462035B2 - Color image forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a developing device to sequentially form toner images of different colors on the surface of an image carrier without superimposing them, and transfer the respective toner images to the surface of a recording medium in an overlapping manner. The present invention relates to a color image forming method for cleaning the surface of an image bearing member by collecting a transfer residual toner attached to the surface of the image bearing member after the transfer of each toner image on a cleaning member.

[0002]

2. Description of the Related Art Copiers, printers, and
In a color image forming apparatus configured as a facsimile machine or a multi-function peripheral thereof, the image carrier is repeatedly used, and therefore the transfer residual toner remaining on the surface of the image carrier after the toner image of each color is transferred is removed. It is necessary to remove and collect with a cleaning member to clean the surface of the image carrier. Therefore, various cleaning devices for cleaning the surface of the image carrier have been proposed and put into practical use, but the conventional cleaning device generally stores the toner collected from the image carrier in a waste toner tank or the like. Then, it is configured to be discarded.

By the way, in recent years, in this type of image forming apparatus, it has been demanded to further reduce the cost and further reduce the amount of toner to be discarded as a part of measures against environmental problems. In view of such a point, if the transfer rate of the toner image from the image carrier to the recording medium is set to 100% to eliminate the residual toner after the transfer, a so-called cleanerless system can be adopted. As a result, not only the toner to be discarded can be eliminated, but also the cleaning device can be omitted, and the image forming system can be simplified and the cost of the image forming device can be reduced. However, at present, it is difficult to set the transfer rate of the toner image to 100%, and there is a problem in terms of reliability.

Therefore, as a second best measure, the transfer residual toner remaining on the surface of the image carrier after the transfer of the toner image is electrostatically and temporarily adhered to the cleaning member to be recovered, and then the recovered toner is A method has been proposed in which the toner is re-deposited electrostatically on the surface of the image carrier that does not affect the formation of the toner image, and the re-deposited toner is electrostatically collected in a developing device and reused. (For example, Japanese Patent Publication No. 61-30
274). This eliminates the need for a waste toner tank for storing the collected toner and a dedicated means for transferring the collected toner to the developing device, so that the cost of the image forming apparatus can be reduced and the toner can be recycled. Therefore, it is possible to eliminate the waste toner.

However, in the color image forming method of the type described at the beginning, toner images of different colors are sequentially formed on the image bearing member, and the transfer residual toner adhering to the image bearing member after each toner image is transferred. Since the toner is collected by the cleaning member, if the transfer residual toner is collected by the cleaning member and then re-adhered to the image carrier, the toner of different colors adheres to the cleaning member in a mixed state. Become. If the toner in such a color mixture state is returned to the surface of the image carrier and collected by the developing device, the developer in the developing device becomes a color mixture state, and depending on the developer, a toner image of a predetermined color is carried on the image carrier. It cannot be formed on the body.

Therefore, the applicant of the present invention collects transfer residual toners of different colors on a plurality of cleaning members, respectively, and re-adheres the collected toners separately to the surface of the image bearing member. There has been proposed a color image forming method in which each color is collected in a developing device containing a developer of each color (Japanese Patent Laid-Open No. 8-160781). However, according to this method, since a plurality of cleaning members are used,
The structure of the image forming apparatus that implements the method is complicated, and the size of the image forming apparatus is large. Further, when carrying out this method, after all the transfer residual toner of each color on the surface of the image carrier is completely collected by each cleaning member,
If the toner of each color is returned to the surface of the image carrier, the time required to form one color image on the recording medium becomes long, and the image forming speed decreases.

Further, in the above-mentioned application, the transfer residual toner of each color is collected in different toner collecting areas in the circumferential direction of one cleaning member, and the collected toner is sequentially reattached to the surface of the image carrier. Methods are also disclosed. According to this method, only one cleaning member is required, and it is possible to prevent the structure of the image forming apparatus from becoming complicated and the size thereof becoming large. However, also in this case, when the transfer residual toner of each color on the surface of the image carrier is completely collected in each toner collecting area of the cleaning member, the toner of each color is re-adhered to the surface of the image carrier, The image forming speed cannot be increased. Further, since the toners of different colors are simultaneously carried on one cleaning member, the toners of the respective colors on the cleaning member may be mixed with each other to cause color mixing.

[0008]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above recognition. A first object of the present invention is to use only one cleaning member and transfer residual toner of each color on the surface of an image carrier. It is an object of the present invention to provide a color image forming method in which the toner can be collected on the cleaning member, and then the collected toner can be reattached to the surface of the image carrier, and the color mixture of the toner on the cleaning member can be prevented.

A second object of the present invention is to provide a color image forming method capable of increasing the image forming speed, in addition to the above-mentioned operation.

A third object of the present invention is to collect the transfer residual toner of each color on the surface of the image carrier on the cleaning member by using only one cleaning member, and then to recover the recovered toner on the surface of the image carrier. It is an object of the present invention to provide a color image forming method which can be adhered and can increase the image forming speed.

[0011]

In order to achieve the first object, the present invention sequentially forms electrostatic latent images for different colors on an image carrier which is rotationally driven, and the electrostatic latent images for the respective colors are sequentially formed. The latent images are sequentially visualized as toner images of different colors by a plurality of developing devices containing developers of different colors respectively, and the toner images of the respective colors are sequentially formed on the same recording medium. Each time a toner image of each color is transferred, the transfer residual toner adhering to the surface of the image carrier after each toner image is transferred is electrostatically collected by one rotating cleaning member to form an image. Clean the surface of the carrier,
After completion of each toner collecting operation, the toner collected by the cleaning member is electrostatically redeposited on the surface portion of the image carrier that does not affect the formation of the next toner image on the surface of the image carrier, and the image is re-deposited. A color image forming method is proposed in which the toners of the respective colors redeposited on the surface of the carrier are electrostatically collected in the respective developing devices containing the developers of the respective colors (claim 1).

In order to achieve the second object of the present invention, in the color image forming method according to the first aspect, when an electrostatic latent image is formed on the image carrier, the electrostatic latent image is formed. Immediately after the rear end of the image forming area in which the latent image is formed passes through the cleaning member, the rear end of the image forming area reaches the cleaning member again as the image bearing member rotates. Re-adhesion operation of the toner from the cleaning member to the surface of the image bearing member is started at a suitable time up to immediately before, and after the operation is started, each color of the surface of the image bearing member which has passed through the cleaning member without being collected by the cleaning member. A color image forming method is proposed in which the transfer residual toner is electrostatically collected in each developing device containing the developer of each color (claim 2).

In this case, in the color image forming method according to the second aspect, when the operation of re-adhering the toner from the cleaning member to the surface of the image carrier is performed, the surface of the cleaning member and the surface of the image carrier are It is advantageous to control the rotation of the cleaning member so that the contact portions of both of them move in the same direction and the linear velocities of both surfaces are different from each other (claim 3).

Further, in the color image forming method according to the third aspect, the operation of re-adhering the toner from the cleaning member to the surface of the image carrier is performed at least at the rear end of the image forming area to the cleaning member again. It is advantageous to carry out all the way (claim 4).

In order to achieve the above-mentioned third object, the present invention sequentially forms electrostatic latent images for different colors on an image carrier which is rotationally driven, and the electrostatic latent images are A plurality of developing devices containing developers of different colors respectively sequentially form visible images as toner images of different colors, and successively transfer the toner images of the respective colors onto the same recording medium. At the same time, each time the toner image of each color is transferred, the transfer residual toner adhered to the surface of the image carrier after the transfer of each toner image is transferred to different toner collecting areas in the circumferential direction of the surface of one rotating cleaning member. When the electrostatic latent image for the toner image formed last on the surface of the image carrier is formed on the image carrier among the plurality of toner images of different colors that are electrostatically collected, An electrostatic latent image is formed From the time immediately after the rear end of the image forming area in the circumferential direction of the image carrier passes through the cleaning member to the time immediately before the rear end of the image forming area reaches the cleaning member again as the image carrier rotates. Then, the operation of re-adhering the toner of the color of the toner image finally formed on the surface of the image carrier to the surface of the image carrier from the cleaning member is started, and the rear end of the image forming area passes through the cleaning member again. After that, the toners of the other colors collected by the cleaning member are reattached to the surface of the image carrier one after another separately, and the toners of the respective colors reattached to the surface of the image carrier and the toner finally formed on the surface of the image carrier. The toner that is the transfer residual toner of the image and that has passed through the cleaning member without being collected by the cleaning member is electrostatically collected in each developing device containing the developer of each color. It proposes an image forming method (claim 5).

At this time, in the color image forming method according to the fifth aspect, when the toner of the color of the toner image finally formed on the surface of the image carrier is reattached from the cleaning member to the surface of the image carrier. When performing the operation, it is advantageous to control the rotation of the cleaning member so that the surface of the cleaning member and the surface of the image carrier move in the same direction at the contact portions of the both, and the linear velocities of the both surfaces are different from each other. (Claim 6).

Further, in the color image forming method according to the sixth aspect, the operation for re-adhering the toner of the color of the toner image finally formed on the surface of the image carrier from the cleaning member to the surface of the image carrier is performed. It is advantageous that at least the rear end of the image forming area of the toner image formed last reaches the cleaning member again (claim 7).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic partial sectional view showing an example of a color image forming apparatus for carrying out the color image forming method according to the present invention. When a print button of an operation unit (not shown) is pressed, the drum-shaped photosensitive body 1 which is one configuration example of the image carrier is rotationally driven in the counterclockwise direction (direction of arrow R) in FIG. 1 by a driving device (not shown). To be done. During this rotation, the photoconductor 1 is neutralized by the static elimination lamp 11 which is an example of the static elimination device, and its surface is initialized. Then, the surface of the photoconductor 1 is changed by the action of the charging roller 2 which is an example of the charging device. It is uniformly charged to a predetermined polarity. In this example, the charging roller 2 is connected to the charging power source E ₁ and uniformly charges the surface of the photoconductor 1 to a negative polarity while rotating in contact with the photoconductor 1. By the action of the charging roller 2, the surface of the photoconductor 1 is charged to, for example, −850V.
As the charging device for uniformly charging the photoconductor 1, a charging device arranged apart from the photoconductor, such as a corona discharger, may be used.

Next, in the exposure unit 3, an exposure scanning device (not shown) performs an optical writing scan using, for example, the light-modulated laser beam L, so that the surface of the photosensitive member 1 has a first electrostatic latent image. An image is formed. here,
It is assumed that the first electrostatic latent image is a yellow toner image latent image. The surface potential of the portion A irradiated with the laser light L forming such an electrostatic latent image is, for example, about −150 V, and the surface potential of the portion B which is the background portion not irradiated with the laser light L is maintained at about −850 V. It As described above, in this example, the charging roller 2 and the exposure scanning device constitute a latent image forming means for forming an electrostatic latent image on the image carrier composed of the photoconductor 1.

A plurality of developing devices 4Y, 4M, are provided in a region downstream of the exposure unit 3 in the rotation direction of the photoconductor 1.
4C and 4B are arranged facing the photoconductor 1. The number of developing devices corresponds to the number of colors of toner images of different colors formed on the photoconductor 1. In this example, four developing devices, that is, first to fourth developing devices, are provided, and each of the developing devices 4Y, 4
The yellow developer YD, the magenta developer MD, the cyan developer CD, and the black developer BD are contained in the developing containers 9Y, 9M, 9C, and 9B of M, 4C, and 4B, respectively. As described above, a plurality of developing devices containing the developers of different colors are provided. In this example, a two-component developer having a toner and a carrier is used as the developer. It is also possible to use a one-component developer having no. In either case, a powdery developer is used.

The developer in each developing container is agitated by the rotation of an agitating member (not shown), and the toner has a predetermined polarity due to friction with the carrier, in this example, the same polarity as the charging polarity for the photoconductor 1. It is negatively charged.

Each of the developing devices 4Y, 4M, 4C and 4B has a developing roller 5Y, 5M, 5C and 5B which is an example of a developer conveying member which is arranged to face the photoconductor 1, and among these developing devices. When one developing device is operating, the other developing device is inactive. In FIG. 1, the first developing device 4Y is in the operating state, and the other developing devices 4M, 4
C and 4B show the state when in the non-operating state.

The developing device in the operating state carries the developer on the peripheral surface of the developing roller by the rotation of the developing roller and is conveyed, and the developer is carried in the developing area between the developing roller and the photosensitive member 1. Carried. On the other hand, the developing device in the non-operating state does not separate from the photosensitive member 1 or the developer is not conveyed by the developing roller, and the developing device is developed in the area between the developing roller and the photosensitive member 1. The agent is not present.

The first electrostatic latent image formed on the photoreceptor 1 as described above is the first electrostatic latent image containing the yellow developer YD.
By the developing device 4Y, a visible image is formed as a yellow toner image. That is, the developing device 4Y is put into operation immediately before the first electrostatic latent image reaches the first developing device 4Y as the photoconductor 1 rotates, and the developing roller 5Y is rotationally driven in the clockwise direction. Then, the yellow developer YD is carried by the developing roller 5Y and conveyed to the developing area. At this time, the developing roller 5Y, the bias power supply YE _2, for example, the same polarity as the charging polarity of the bias voltage of the photosensitive member 1 of about -600V is applied. Therefore, in the developing area of the first developing device 4Y, the yellow toner in the developer YD electrostatically moves and adheres to the electrostatic latent image on the photoconductor 1. The yellow toner charged with the same negative polarity as the charging polarity of the photoconductor 1 adheres to the surface A of the photoconductor that has been irradiated with the laser light, that is, the electrostatic latent image, and the electrostatic latent image becomes a yellow toner image. It is visualized. In FIG. 1, each toner T forming a toner image is schematically shown in an enlarged manner. As described above, the image forming apparatus of this example employs the reversal development method (negative / positive development method).

The toner image is transferred to another developing device 4M, 4M.
When passing through C and 4B, since these developing devices are in the non-operating state, the toner of the developer accommodated in these developing devices does not adhere to the surface portion of the photoconductor, and the toner of the yellow toner image is not attached. Will not be collected by these developing devices. In the illustrated example, the application of the bias voltage is cut off to the developing roller of the developing device in the non-operating state, and the rotation of each developing roller is stopped. The developing roller of the developing device in the operating state rotates clockwise, and the bias voltage is applied only to the developing roller.

On the other hand, the photosensitive member 1 is better than the plurality of developing devices.
A transfer drum 6 is arranged to face the photoconductor 1 on the downstream side in the rotation direction of. The transfer drum 6 is rotationally driven in the clockwise direction in FIG. 1, and a transfer sheet P, which is an example of a recording medium fed from the sheet feeding device 20, is wound around the peripheral surface of the transfer drum 6 in a close contact state, The tip is locked to the transfer drum 6 by a clamp (not shown). Photoconductor 1
When the front end of the yellow toner image formed on the transfer paper P coincides with the front end of the transfer paper P, the transfer paper P is fed by the paper feeding device 20.
Then, it is fed to the clamp of the transfer drum 6 and wound around the peripheral surface of the transfer drum.

The diameter of the transfer drum 6 is larger than that of the photoconductor 1, and the total length of the transfer paper P wound around the transfer drum 6 is longer than the circumference of the photoconductor 1. Although common, in FIG. 1, for convenience, the diameters of the photosensitive member 1 and the transfer drum 6 are shown to be substantially equal (the same applies in FIG. 15).

When the yellow toner image formed on the photoconductor 1 reaches the transfer portion 8 which is a contact area between the photoconductor 1 and the transfer paper P on the transfer drum 6, it is arranged inside the transfer drum 6. The yellow toner image on the photoconductor 1 is transferred onto the transfer paper on the transfer drum which is in contact with the photoconductor 1 by the discharge action of the transfer charger 7 which is an example of the transfer device.
By the discharge from the charge wire of the transfer charger 7, the toner on the photoconductor 1 is electrostatically attracted to the transfer paper side, and the toner image is transferred onto the transfer paper.

As described above, the yellow toner image on the photoconductor 1 is transferred to the transfer paper P at the transfer portion 8, but is not transferred to the transfer paper P on the surface of the photoconductor after the transfer of the toner image. The remaining toner T ₁ is attached. Although the transfer residual toner T ₁ is also schematically enlarged in FIG. 1, the transfer residual toner T ₁ is an example of a cleaning member that rotates while contacting the peripheral surface of the photoconductor 1. The surface of the roller 10 is electrostatically collected as described later, and the surface of the photoconductor 1 is cleaned thereby. The transfer residual toner T ₁ on the photoconductor is cleaned by the cleaning roller 10 at the cleaning portion 15 at the contact portion between the two. The surface portion of the photoconductor whose surface has been cleaned by the cleaning roller 10 is the static elimination lamp 1.
The static elimination action is performed by 1, the surface potential is returned to the reference value, and the surface is initialized.

The transfer residual toner adhering to the surface of the photoconductor after the transfer of the yellow toner image is collected by the cleaning roller 10 as described above. After the collecting operation is completed, the toner collected by the cleaning roller 10 is collected. Are again electrostatically returned to the surface of the photoconductor 1 and redeposited on the photoconductor surface, and the redeposited toner is electrostatically collected by the developing device 4Y. In this way, by reattaching the toner on the cleaning roller 10 to the surface of the photoconductor 1, the yellow toner does not exist on the surface of the cleaning roller 10. The configuration and operation relating to such toner recovery and reattachment of the toner to the photosensitive member 1 will be described later in detail.

The yellow toner image is transferred onto the transfer paper as described above. Then, in the same manner as described above, the charge-eliminated surface of the photoconductor is charged by the charging roller 2 and the laser is applied in the same manner as described above. A second electrostatic latent image for a magenta toner image is formed by exposure scanning with the light L. This second electrostatic latent image is visualized as a magenta toner image by the second developing device 4M which has been activated, in the same manner as in the above-mentioned first developing device 4Y. The developing roller 5M of the second developing device 4M, the bias power supply ME ₂ eg bias voltage of -600V is applied, and the developing roller 5M is rotated clockwise, the carried on the developing roller 5M the magenta The second electrostatic latent image is visualized as a magenta toner image by the developing agent. At this time, the other developing devices 4Y, 4C, 4B are in the non-operating state, and the bias voltage is applied to the developing rollers 5Y, 5C, 5B.
The rotation of each developing roller 5Y, 5C, 5B is stopped.

The magenta toner image is transferred onto the transfer paper P clamped on the transfer drum 6 rotating in the clockwise direction from the previously transferred yellow toner image in an overlapping manner.

The transfer residual toner adhered on the photoconductor 1 after the transfer of the toner image is electrostatically collected on the cleaning roller 10 which rotates in contact with the surface of the photoconductor 1, and the surface of the photoconductor 1 is cleaned. Then, the surface of the photoconductor cleaned by the cleaning roller 10 is subjected to static elimination action by the static elimination lamp 11. At the time of collecting the toner, the yellow toner does not already exist on the surface of the cleaning roller 10, so that the toners of different colors do not mix on the cleaning roller 10. The magenta toner collected by the cleaning roller 10 is also electrostatically returned to the photoconductor 1 and reattached to the surface of the photoconductor 1, so that the cleaning roller 10
There is no magenta toner on the upper side. The redeposited toner is electrostatically collected by the second developing device 4M.

Then, in exactly the same manner, a third electrostatic latent image is formed on the surface of the photoconductor 1, and this is visualized as a cyan toner image by the activated third developing device 4C. This is transferred onto the transfer paper P on the transfer drum 6 so as to be superimposed on the previously transferred yellow and magenta toner images. The untransferred toner attached on the photoconductor after the transfer is also electrostatically collected on the cleaning roller 10 which is in contact with the surface of the photoconductor 1 and rotates to clean the surface of the photoconductor. At this time as well, since toners of other colors do not exist on the cleaning roller 10, toner color mixture does not occur. The surface of the photoconductor after cleaning is subjected to static elimination action by the static elimination lamp 11. The cyan toner collected by the cleaning roller 10 is also electrostatically returned onto the photoconductor 1 and redeposited on the photoconductor surface, and then electrostatically collected by the third developing device 4C.

In the same manner, a fourth electrostatic latent image is formed on the photosensitive member, and this is visualized as a black toner image by the fourth developing device 4B which is in an operating state.
This is transferred onto the transfer paper P on the transfer drum 6 so as to be superposed on the previously transferred toner image, and the transfer residual toner adhering to the photoconductor 1 after the transfer of the toner image comes into contact with the photoconductor surface and rotates. It is electrostatically collected by the cleaning roller 10. Also at this time, color mixing due to toners of different colors does not occur. Further, the black recovered toner is also electrostatically returned onto the photoconductor 1 and electrostatically recovered by the fourth developing device 4B.

As described above, in the illustrated color image forming method, electrostatic latent images for different colors are sequentially formed on the image carrier composed of the photosensitive member 1 which is rotationally driven, and the electrostatic latent images are formed. To the developers YD, MD, and C of different colors.
A plurality of developing devices 4Y, 4M, 4C containing D and BD,
4B, the toner images of different colors are sequentially visualized, and the toner images of the respective colors are sequentially superimposed and transferred onto the same recording medium, that is, the same transfer paper, and the toner images of the respective colors are transferred. The transfer residual toner adhering to the surface of the image carrier after the transfer of each toner image is electrostatically collected by one rotating cleaning member to clean the surface of the image carrier.

By transferring the four color toner images onto the transfer paper P on the transfer drum 6, a full color image is formed on the surface of the transfer paper. The transfer paper P on which the full-color image is formed in this way is released from the above-mentioned clamp and the separation claw 1
2 and the action of the separation chargers 12A and 12B,
The transfer drum 6 is separated from the transfer drum 6 as indicated by an arrow Q, and is subsequently conveyed to a fixing device (not shown), where the full-color toner image on the transfer paper is fixed on the transfer paper by the action of heat and pressure. In this way, a copy paper on which a full-color image is formed is obtained.

When the toner images of the respective colors formed on the surface of the photoconductor are successively transferred onto the transfer paper on the transfer drum 6, the voltage applied to the transfer charger 7 is sequentially increased to surely transfer the toner images to the transfer paper. Allow transfer to P.

Next, the transfer residual toner of each color is collected on the cleaning roller 10 as described above, then the toner of each color is re-adhered to the surface of the photoconductor, and the re-adhered toner is collected to each developing device. And the details of its action.

The cleaning roller 10 is composed of, for example, a central shaft 13 made of a conductive metal and an elastic body 14 having a medium resistance such as foam or solid rubber fixed around the central shaft 13. Is housed in a case (not shown), and is rotatably supported on the front and rear side walls of the case. Cleaning roller 10
Is a charging roller 2 and developing rollers 5Y, 5M, 5C, 5B
And the transfer drum 6 and the photosensitive drum 1 in parallel.

Here, of the four color toner images formed on the photoconductor 1, the yellow toner image will be considered. In the region where the developing roller 5Y of the first developing device 4Y and the photoconductor 1 face each other. Most of the toner T of the yellow toner image traveling from a certain developing region to the transfer portion 8 has a charging polarity at the time of development, that is, a negative polarity toner in this example. On the other hand, when the toner image is transferred by the transfer charger 7, since the toner is given a charge of a positive polarity opposite to the charging polarity of the toner at the time of development, the toner is transferred onto the photoconductor 1 after the toner image is transferred. The transfer residual toner T ₁ that adheres is a toner in which positive polarity toner and negative polarity toner are mixed, and in general, the positive polarity toner is more common. As described above, the transfer residual toner T ₁ is transferred to the cleaning portion 15 by the cleaning roller 10, that is, the contact portion between the cleaning roller 10 and the photoconductor 1 in a state where the toners of both positive and negative polarities are mixed. It is. The same applies to transfer residual toner that adheres to the surface of the photoconductor after the transfer of toner images of other colors.

[0043] In this example, the cleaning roller 10, when collecting the residual toner T ₁ of the the photosensitive member 1, the counterclockwise direction in FIG. 1, i.e. both surfaces at the contact portion of the cleaning roller 10 and the photosensitive member 1 Are driven to rotate in the opposite direction, and the cleaning roller 10 rotates while sliding on the surface of the photoconductor 1. The cleaning roller 10 is pressed against the photosensitive member 1 so that the elastic member 14 is elastically deformed by the photosensitive member 1. As shown in FIG. 2, a nip area N is formed at this pressed portion. This nip area N serves as a cleaning section. The width of the nip region N in the circumferential direction of the photoconductor is, for example, about 1 mm, which is exaggerated in FIG.

In the nip region N, the transfer residual toner T ₁ having both positive and negative polarities is transferred to the cleaning roller 1.
By the frictional action from 0 and the photoconductor 1, the toner is triboelectrically charged so that the toner has a regular first polarity (negative polarity in this example) that is the same as the charging polarity of the toner during development.
The transfer residual toner T ₁ is made to have a negative polarity, which is the charging polarity during development.

[0045] Returning to FIG. 1, when recovering the residual toner T ₁ of the the photosensitive member 1 to the cleaning roller 10, the central axis 13 of the cleaning roller 10, the toner is frictionally charged by the cleaning roller 10 A second polarity opposite to the charging polarity (first polarity), in this example, a positive polarity voltage, for example, +200 V, is applied by the cleaning roller power supply E ₃ . Therefore, the transfer unit 8
The residual toner after the transfer of the toner image, that is, the residual toner T ₁ after transfer is electrostatically attracted to the cleaning roller 10 to which a positive polarity voltage is applied, and adheres to the surface of the cleaning roller 10 and is collected. It

The potential of the surface of the photosensitive member 1 which has passed through the transfer charger 7 is, for example, about zero or -50V due to the influence of the discharge of the transfer charger, but the voltage of the second polarity of + 200V is applied. a cleaning roller 10 being applied, the potential difference between the surface of the photoreceptor residual toner T ₁ is attached, the residual toner T ₁ charged to the first polarity negative, the surface of the cleaning roller 10 Be electrostatically attracted to. As a result, the surface of the photoconductor 1 is brought into a cleaning state.

In this way, the cleaning roller 10 rotating in contact with the photoconductor 1 electrostatically attracts the transfer residual toner on the photoconductor 1 toward the cleaning roller 10. The above voltage is applied so that an electric field that can be generated is formed.

[0048] FIGS. 3 to 10, the residual toner T ₁ of the yellow on the photosensitive member 1 is collected by the cleaning roller 10, and then allowed to reattach the collected toner T ₂ on the surface of the photosensitive member 1, developing the FIG. 3 is an explanatory diagram showing an example of an operation of collecting in the apparatus 4Y. Among these drawings, FIG. 3 shows that the toner image on the photoconductor 1 is transferred to the transfer paper P on the transfer drum 6, and the transfer residual toner T ₁ FIG. 3 is a schematic view showing a state in which is collected on the surface of the cleaning roller 10.

In FIGS. 3 to 10, the toner collected on the cleaning roller 10 is indicated by the reference symbol T ₂ , and the toner reattached to the photosensitive member 1 is indicated by T ₃ . Further, the toner on the photoconductor 1 or the cleaning roller 10 is schematically shown in an enlarged manner, and in these figures,
Charging roller 2, developing roller and cleaning roller 10
Symbols + and-appearing to indicate positive and negative polarities of the voltages applied to them, respectively. Similarly, FIG.
In the figure, the + and-signs attached to the toner indicate the charge polarity of the toner.

As shown in FIG. 3, the surface portion of the photosensitive member 1 cleaned by the cleaning roller 10 is neutralized by the static elimination lamp 11, and the surface potential thereof is lowered to the reference value. The surface of the photoconductor that has been subjected to the static elimination is continuously charged by the charging roller 2 and the image forming operation is continued.

While performing the above-described operation, one sheet of yellow toner image is transferred to the photosensitive member 1 while the photosensitive member 1 is rotated several times.
It is formed on the transfer drum 6 and is transferred onto the transfer paper P clamped on the transfer drum 6. The circumferential area on the photoconductor 1 on which the toner image is formed is the image forming area.

In FIG. 3, the image forming area on which the yellow toner image is formed is denoted by reference numeral Y1, and the tip of the image forming area in the circumferential direction of the photoconductor, that is, the most downstream position in the image forming area Y1 in the photoconductor rotating direction. Is denoted by reference numeral Y2. Similarly, in FIG. 4, reference numeral Y3 is attached to the rear end of the image forming area Y1 in the circumferential direction of the photoconductor, that is, the most upstream position in the image forming area Y1 in the photoconductor rotating direction.

At a time point slightly before the time point shown in FIG. 3, when the leading edge Y2 of the image forming area Y1 reaches the cleaning roller 10, the operation of collecting the transfer residual toner T ₁ on the cleaning roller 10 is started. In the examples shown in FIGS. 3 to 10, the rear end Y3 of the image forming area Y1 is
As shown in FIG. 6, the operation of collecting the transfer residual toner is continued until the cleaning roller 10 is reached. The same applies to the transfer residual toner after the toner images of other colors are transferred.

Here, as described above, the cleaning member composed of the cleaning roller 10 electrostatically and temporarily transfers the transfer residual toner T ₁ remaining on the photoconductor 1 after the transfer of the yellow toner image while rotating. The surface of the photoconductor 1 is collected and cleaned. Then, the cleaning member rotates and collects the collected toner T ₂ on a surface portion that does not affect the formation of the electrostatic latent image on the image carrier. Reattach electrically.

That is, as shown in FIG. 4, when the rear end Y3 of the image forming area Y1 in the circumferential direction of the photoconductor passes the charging roller 2, the charging roller 2 is separated from the surface of the photoconductor 1 at this time (see FIG. 5). At the same time, the switch S ₁ shown in FIG. 1 is switched to turn off the voltage application to the charging roller 2.

When the trailing edge Y3 of the image forming area of the yellow toner image passes the developing roller 5Y of the first developing device 4Y as shown in FIG. 5, the switch is switched,
The developing roller 5Y is connected to the power source YE ₅ shown in FIG. 1, and the developing roller 5Y has a second positive polarity opposite to the charging polarity of the toner so that the toner does not adhere to the photoconductor 1.
A voltage having a polarity of, for example, a voltage of +150 V is applied.
Subsequently, when the trailing edge Y3 of the image forming area of the yellow toner image passes the transfer portion 8, the operation of the transfer charger 7 (FIG. 1) is stopped at this time.

When the trailing edge Y3 of the image forming area Y1 reaches the cleaning portion of the cleaning roller 10 as shown in FIG. The collection, that is, the cleaning of the photoconductor is completed.

The toner T ₂ thus collected on the cleaning roller 10 is reattached to the surface portion of the photosensitive member which does not affect the next magenta toner image formation. That is, as shown in FIG. 6, when the trailing edge Y3 of the image forming area after the yellow toner image is transferred onto the transfer paper passes through the cleaning roller 10, the switch is switched, and the cleaning roller 10 is shown in FIG. A voltage of the first negative polarity, which is the same as the charge polarity of the toner frictionally charged by the cleaning roller 10, is connected to the central axis 13 of the cleaning roller 10 connected to the power source YE ₄ .
For example, a voltage of -3000V is applied. At this time, the cleaning roller 10 of this example is also switched in its rotation direction. Rotating cleaning roller 10 and photoconductor 1
An electric field in the direction in which the collected toner T ₂ on the cleaning roller 10 is discharged toward the photoconductor 1 is formed between the non-image forming area Z (FIG. 7).

Due to the electric field, the yellow toner T ₂ temporarily collected on the cleaning roller 10 is reattached and returned to the non-image forming area Z on the photosensitive member 1 as shown in FIG. As shown in FIG. 8, the re-adhered toner T ₃ is discharged from the charge eliminating lamp 1 by the subsequent rotation of the photoreceptor 1.
1 and the charging roller 2 separated from the photosensitive member 1,
As shown in FIG. 5, the developing roller 5Y of the first developing device 4Y is reached. At this time, as described above, since the voltage of the second polarity opposite to the charging polarity of the toner at the time of development, that is, the positive polarity voltage is applied to the developing roller 5Y, the toner is re-deposited on the photoconductor 1. Minus polarity yellow toner T
₃ is electrostatically transferred to the developing roller 5Y side and is collected in the developer in the developing device 4Y. in this way,
The toner redeposited on the photoconductor 1 is electrostatically collected by the developing device 4Y containing the developer YD of the same color as the toner.

The toner collected in the first developing device 4Y is reused in the developing device 4Y for visualizing the electrostatic latent image. Toner T ₃ redeposited on the photoconductor 1
Are collected in a developing device containing a developer of the same color, so that the collected toner can be reused in the developing device without any trouble. The color of the toner image formed by the reused toner is not disturbed by the color mixture. In this way, the waste toner can be eliminated, and it is not necessary to provide a toner conveying pipe for returning the toner collected by the cleaning roller to the developing device.

When the cleaning roller 10 finishes returning the collected toner T ₂ onto the photoconductor 1, as shown in FIG. 9, the toner T ₃ from the cleaning roller 10 is more exposed than the area Z to which the toner T ₃ is reattached. A second electrostatic latent image for the next magenta toner image is formed in the image forming area M1 on the upstream side in the body rotation direction. That is, when the image forming area M1 is subjected to the charge removing function of the charge removing lamp 11, and subsequently the tip M2 of the image forming area M1 for the magenta toner image in the circumferential direction of the photoconductor reaches the charging roller 2, the charging roller 2 is The image forming area M1 is contacted with the photoreceptor 1 (FIG. 9), the image forming area M1 is charged with a negative polarity, and the charged surface is irradiated with the laser beam L. In this manner, the second electrostatic latent image is formed in the image forming area M1 in the same manner as described above, and this is visualized as a magenta toner image by the second developing device 4M as described above. It

This magenta toner image is transferred onto the transfer paper P on the transfer drum 6. The transfer residual toner adhering to the photosensitive member after the transfer is also cleaned in the same manner as described above. Electrostatically recovered to 10. That is, as shown in FIG. 8, after the yellow toner on the cleaning roller 10 has been redeposited on the surface of the photoconductor 1, the front end M2 of the image forming area M1 that has passed through the transfer portion 8 as shown in FIG. The voltage of the second positive polarity is applied to the cleaning roller 10 by the power source E ₃ (FIG. 1) until just before reaching the cleaning roller 10 which is in pressure contact with the surface of the photoconductor 1. The transfer residual toner of the magenta toner image is electrostatically collected on the surface of the cleaning roller 10. When the collection is completed, a voltage of the first negative polarity is applied to the cleaning roller 10 by the power source E ₄ (FIG. 1), and the magenta toner collected by the cleaning roller 10 is removed from the image forming area M1 of the magenta toner image. Is also redeposited on the non-image forming area on the upstream side in the rotation direction of the photoconductor, that is, on the surface part of the photoconductor that does not affect the formation of the next cyan toner image, and this applies a second positive bias voltage. The magenta toner is electrostatically drawn by the developed developing roller 5M, and the magenta toner is collected by the second developing device 4M and reused for visualizing the electrostatic latent image.

In exactly the same manner, after the cyan toner image and the black toner image sequentially formed on the photoconductor 1 are transferred to the transfer paper P, the respective transfer residual toners adhering to the photoconductor 1 are sequentially cleaned. Are electrostatically recovered, and the recovered toner is electrostatically returned to the surface of the photoconductor that does not affect the formation of the next toner image and redeposited on the surface of the photoconductor. The third and fourth developing devices 4C and 4B are electrostatically recovered and reused.
Since any of the re-adhered toners is returned to each developing device containing the same color developer, the collected toners can be reused without causing color mixture and the image quality of the toner image formed on the photoconductor is improved. There is no risk of deterioration.

FIG. 1 shows power supplies YE ₂ and YE ₅ for applying a voltage to the developing roller 5Y of the first developing device 4Y, which correspond to the power supplies in the other developing devices 4M to 4B.
Are denoted by reference numerals _{ME 2, CE 2, BE 2} , ME 5, CE 5, BE 5 respectively, actuation of these, like the respective power YE _2, YE ₅ in the first developing device 4Y as described above To do.

As described above, in the color image forming method of this embodiment, each time the toner collecting operation for the cleaning member is completed,
The toner collected by the cleaning member is electrostatically redeposited on the surface portion of the image carrier that does not affect the formation of the next toner image on the surface of the image carrier, and the toner of each color redeposited on the surface of the image carrier is attached. The toner is electrostatically collected in each developing device containing the developer of each color.
This is an example of an embodiment corresponding to claim 1.

According to the above construction, by using only one cleaning member, the transfer residual toner of each color on the image carrier is collected by the cleaning member to clean the surface of the image carrier, and the once collected color of each color is collected. The toner can be returned as it is to the developing device containing the developer of the same color as the toner and reused. Moreover, since the toners of the respective colors collected on the cleaning member are returned to the surface of the image carrier after the completion of the collecting operation, the toners of different colors do not adhere to the cleaning member at the same time. It is possible to prevent the trouble that the toners of different colors are mixed on the cleaning member and prevent the deterioration of the quality of the toner image due to the color mixture of the toners.

As described above, the transfer residual toner T ₁ on the photosensitive member 1 that has passed through the transfer portion 8 is the toner (different polarity toner) charged to the opposite polarity to the charging polarity of the toner at the time of development. In this example, the different polarity toner is aligned with the first polarity, which is the charge polarity of the toner during development, by frictional charging with the cleaning roller 10.

However, the nip area N shown in FIG.
It is difficult to completely align the charge polarities of the transfer residual toners existing in the above, and there may be some toners that remain the charge polarities opposite to the charge polarities of the toners at the time of development, that is, different polarity toners. At the time of collecting each transfer residual toner, the voltage of the second polarity opposite to the charging polarity of the toner at the time of development is applied to the cleaning roller 10 as described above, and has the first polarity at the time of development. The toner is electrostatically transferred to the cleaning roller 10 and is collected by the cleaning roller 10. At this time, toner having a polarity opposite to the charging polarity at the time of development (different polarity toner) is generated. If so, this toner also adheres to the cleaning roller 10 due to the mechanical scraping force received from the cleaning roller 10. If the different polarity toner is transferred to the photoconductor 1 during the toner collecting operation from the photoconductor 1, the background stain on the image and the charge roller 2 are caused.

Therefore, in the image forming apparatus of this embodiment, when the transfer residual toner T ₁ is collected from the photoconductor 1 to the cleaning roller 10, the contact area between the photoconductor 1 and the cleaning roller 10, as shown in FIG. That is, in the nip region N where these are pressed against each other, the rotation direction of the cleaning roller 10 is controlled so that both surfaces move in opposite directions (counter direction), and the cleaning roller 10 rotates less than one rotation. Then, the rotation of the cleaning roller 10 is controlled so that the transfer roller residual toner on the photoconductor 1 is collected by the cleaning roller 10. When the cleaning roller 10 rotates less than one rotation, the operation of collecting each transfer residual toner on the photoconductor 1 is completed.

With this configuration, the cleaning roller 10
The toner collected in step 1 does not come into contact with the photoconductor 1 again during the toner collecting operation. Moreover, it is possible to prevent the different polarity toner collected on the cleaning roller 10 from being electrostatically transferred to the surface of the photoconductor 1 after cleaning during the toner collecting operation.

If the cleaning roller 10 is rotated in the nip region N with the photoconductor 1 in the direction in which they move in the same direction as shown by the chain line arrow b in FIG. 2 when collecting the residual toner after transfer. As a result, the collected toner T ₄ is present on the cleaning roller 10 on the downstream side in the rotation direction of the photoconductor 1, and if the toner T ₄ is a different polarity toner that remains charged in the positive polarity, the cleaning roller 10 is At the time of collecting the toner, since the same positive polarity voltage as that is applied, the positive polarity toner T ₄ is electrostatically attracted toward the photoconductor 1 and adheres to the surface of the photoconductor. In this case, the cleaning failure of the photoconductor 1 occurs, and the toner image subsequently formed has background stains.

In order to eliminate such a problem, when the cleaning roller 10 collects the transfer residual toner as described above, these rotate in the counter direction with respect to the photoconductor 1, that is, in the direction of the solid arrow a in FIG. The rotation directions of the two are set so as to do so.

Further, at that time, if the cleaning roller 10 is rotated once or more to collect the transfer residual toner from the photoconductor 1, the toner collected by the cleaning roller 10 has a positive polarity and a different polarity. When the toner T ₄ exists, when the toner T ₄ approaches the photoconductor 1 again or comes into contact with the photoconductor 1, the toner T ₄ adheres to the photoconductor 1 and cleaning failure of the photoconductor 1 occurs. Therefore, in this example, the toner collecting operation from the photoconductor 1 to the cleaning roller 10 is completed while the cleaning roller 10 is rotationally driven for less than one rotation.

According to the above construction, the cleaning roller 1
It is possible to make it difficult for the toner (different polarity toner) having a polarity opposite to the charging polarity at the time of development collected to 0 (different polarity toner) to be transferred to the photoconductor 1.

When the collected toner on the cleaning roller 10 is reattached to the photoconductor 1, the cleaning roller may be rotated in any direction, but in the present example, the photoconductor 1 is rotated.
In the nip area N between and, the rotation direction of the cleaning roller 10 is controlled so that the cleaning roller and the photosensitive member 1 rotate in the same direction (the direction of the chain line arrow b in FIG. 2), and the rotation speed thereof is higher than that at the time of toner collection. Also raise the photoconductor 1
The toner is re-adhered to the photoconductor 1 efficiently in a short time by rotating at a speed higher than the peripheral speed of. According to experiments, when the toner on the cleaning roller 10 is returned to the surface of the photoconductor, it is better to rotate the cleaning roller 10 in such a direction that both surfaces move in the same direction at their contact portions. The re-adhesion effect of the toner on the surface of No. 1 could be enhanced.

By the way, in the above-described embodiment, after all the transfer residual toner T ₁ attached to the surface of the photoconductor is completely collected by the cleaning roller 10, the toner on the cleaning roller is reattached to the surface of the photoconductor. Therefore, as can be seen from FIG. 8 and FIG. 9, the area Z rearward in the rotation direction of the photoconductor with respect to the rear end of the image forming area of each toner image.
In the region further behind the electrostatic latent image for the toner image of the next color must be formed. For this reason, a large area where a toner image is not formed is formed between the image forming areas where the toner images of the respective colors are formed, which inevitably reduces the image forming speed.

Therefore, in the example shown in FIGS. 11 to 14,
As compared with the above example, the cleaning roller 10 to the photosensitive member 1
The timing of re-adhering the toner to the surface of the sheet is accelerated so as to prevent the above-mentioned problems.

FIG. 11 shows the cleaning roller 10 in which the rear end Y3 of the image forming area Y1 of the yellow toner image is in contact with the surface of the photoconductor to collect the yellow transfer residual toner T _1.
This shows the state immediately after passing through the portion, that is, the cleaning unit 15. At this time, the image forming area Y1
On the other hand, the charging operation is performed by the charging roller 2 which is in contact with the surface of the photoconductor 1 and rotates, and the charging surface is irradiated with the laser beam L to form a first electrostatic latent image. The electrostatic latent image is visualized as a yellow toner image by the developing device 4Y, and the toner image is transferred onto the transfer paper P on the transfer drum 6.

On the other hand, FIG. 12 shows the above-mentioned image forming area Y1.
The rear end Y3 reaches the charging roller 2 as the photosensitive body 1 rotates, and at this time, the charging operation of the charging roller 2 to the photosensitive body 1 is completed and the charging roller 2 is separated from the photosensitive body 1. ing.

Further, FIG. 13 shows the rear end Y of the image forming area Y1.
3 shows a state after 3 has passed through the developing area between the developing roller 5Y and the photoconductor 1, and the rear end Y3 is the developing device 4
When it passes Y, the developing operation by the developing device 4Y is completed, and the positive bias voltage of the second polarity is applied to the developing roller 5Y.

Subsequently, the rear end Y3 of the image forming area Y1 is
It passes through the developing device 4M, 4C, 4B (FIG. 1) in the non-operating state and passes through the transfer portion 8. Subsequently, the rear end Y3 reaches the cleaning portion 15 where the cleaning roller 10 and the photosensitive member 1 are in pressure contact with each other again, but FIG. 14 shows a state immediately before the rear end Y3 reaches the cleaning roller 10 again.

The operation described above is the same as that described above with reference to FIGS. The difference is that
When the first circumferential latent image Y3 of the image forming area Y1 where the electrostatic latent image is formed passes through the cleaning roller 10 when the first electrostatic latent image is formed on the photoconductor 1, That is, from the time point shown in FIG. 11 to the time point immediately before the trailing edge Y3 of the image forming area Y1 reaches the cleaning roller 10 again as the photoconductor 1 rotates, that is, at the time point shown in FIG. Is to start the re-adhesion operation of the toner onto the surface of the photoconductor 1.

Now, assuming that the re-adhesion operation of the toner from the cleaning roller 10 to the photosensitive member 1 is started from the time point shown in FIG. Then, up to this point, as described above, the cleaning roller 10 is rotationally driven in the counterclockwise direction and is rotated in the direction opposite to the moving direction of the photoconductor 1 at the contact portion with the photoconductor 1. A voltage having a second polarity opposite to the charging polarity of the transfer residual toner T ₁ frictionally charged between the cleaning roller 10 and the photosensitive member 1 is applied to the cleaning roller 10.

On the other hand, when the state shown in FIG. 11 is reached,
A voltage having a first polarity that is the same as the charging polarity of the collected toner T ₂ , that is, a voltage of a negative polarity is applied to the cleaning roller 10, and the rotation direction of the cleaning roller 10 is switched, and the cleaning roller 10 concerned is switched. The contact portion 10 with the photoconductor 1 is rotationally driven in a direction in which its surface moves in the same direction as the surface of the photoconductor. As a result, the toner T ₂ collected on the surface of the cleaning roller 10 starts to electrostatically transfer to the surface of the photoconductor 1 and re-adheres to the surface of the photoconductor 1. As described above, by rotating the cleaning roller 10 in the forward direction with respect to the photoconductor 1, the toner can be efficiently reattached to the surface of the photoconductor.

The toner T ₃ redeposited on the surface of the photoconductor is electrostatically collected by the developing roller 5Y when it reaches the developing device 4Y as the photoconductor 1 rotates, as in the previous example.

In this example, since the re-adhesion operation of the toner from the cleaning roller 10 to the photosensitive member 1 is started from the time point shown in FIG. 11, even after the re-adhesion operation is started,
The transfer residual toner T ₁ that has passed through the transfer portion 8 is conveyed while being carried on the surface of the photosensitive member 1 in a region where the cleaning roller 10 is pressed against the surface of the photosensitive member 1. This continues until the trailing edge Y3 of the image forming area Y1 reaches the portion of the cleaning roller 10 again, that is, immediately after the time point shown in FIG. As described below, the transfer residual toner T ₁ sent to the portion of the cleaning roller 10 is as described below.
It is not collected by the cleaning roller 10 that has already started the redeposition operation, and passes through the cleaning roller 10.

As described above, the cleaning roller 10 after the start of the redeposition operation is rotated so as to move in the same direction as the surface of the photoconductor 1 at the contact portion with the photoconductor 1, but the cleaning roller 10 is further cleaned. The rotation of the cleaning roller 10 is controlled so that the linear velocities of both surfaces of the roller 10 and the photoconductor 1 are different from each other. For example, the rotation speed of the cleaning roller 10 is set so that the peripheral speed of the surface of the cleaning roller 10 is faster than the peripheral speed of the surface of the photoconductor 1, or conversely, the linear speed of the surface of the cleaning roller 10 is set to the photoconductor. The rotation speed of the cleaning roller 10 is set so as to be slower than the linear speed of the surface of No. 1.

[0088] Thus, when in any case where the residual toner T ₁ of the the photosensitive member 1 passes through the site of the cleaning roller 10, subjected to rubbing action from the photoreceptor 1 and the cleaning roller 10, thereby, the cleaning roller 10 Of the transfer residual toner T ₁
Is triboelectrically charged to a first polarity that is the same as the charging polarity of the toner at the time of development, that is, a negative polarity, and the charging polarity is made uniform. At this time, the first polarity, that is, a negative voltage is applied to the cleaning roller 10, and the surface potential of the photoconductor 1 is, for example, 0 V as described above. T ₁ passes through here without being collected by the cleaning roller 10. The larger the peripheral speeds of the surface of the cleaning roller 10 and the surface of the photoconductor 1 are, the more the effect of charging the transfer residual toner T ₁ to the first polarity (minus) can be enhanced, and the linear velocity ratio between the two is approximately. If it is set to 1.2 times or more, the transfer residual toner T ₁ can be almost completely charged to the negative.

As described above, the cleaning roller 10
The transfer residual toner that has passed through reaches the developing device 4Y as the photoconductor 1 rotates, and at this time, the developing roller 5Y has a second polarity voltage, that is, a positive polarity voltage (+150 V).
Is applied, the transfer residual toner is efficiently electrostatically collected by the developing device 4Y, and the surface of the photoconductor after passing through the developing device 4Y is cleaned (see FIG. 14). The yellow toner collected in the developing device 4Y is also effectively reused in the developing device 4Y. The photoconductor 1 further rotates counterclockwise from the state shown in FIG. 14, and the rear end Y3 of the image forming area Y1 again becomes the developing device 4 again.
When passing Y, all the transfer residual toner on the image forming area Y1 is completely collected by the developing device 4Y, and the cleaning of the surface is finished.

In this way, the cleaning roller 10
After the re-adhesion operation of the toner onto the surface of the photoconductor 1 is started, the yellow transfer residual toner on the surface of the photoconductor 1 that has not been collected by the cleaning roller 10 and has passed through the cleaning roller 10 Developer YD (Fig. 1)
Can be electrostatically collected in the developing device 4Y housing therein. When the collecting operation is completed, this is detected by a detecting means (not shown), and the developing device 4Y is deactivated.

Immediately after the time point shown in FIG. 14, the trailing edge Y3 of the image forming area Y1 passes through the portion of the cleaning roller 10, and when the toner is reattached from the cleaning roller 10 to the surface of the photosensitive member 1 at this time. The operation ends. At this time, the rotation direction of the cleaning roller 10 is switched to the counterclockwise direction, a positive voltage having the second polarity is applied to the cleaning roller 10, and the next magenta toner image is formed in the image forming area M1. When the leading end M2 of the photoconductor rotating direction passes through the cleaning roller 10 and then the leading end M2 reaches the charging roller 2, the charging roller 2 comes into contact with the surface of the photoconductor 1 to start charging the image forming area M1. And the charged surface is irradiated with the laser beam L,
The second electrostatic latent image formed by this is visualized as a magenta toner image by the developing device 4M in the activated state. At this time, other developing devices 4Y, 4C, 4B
Is inactive. Hereinafter, the image forming operation described above is continued. Then, the transfer residual toner after the transfer of the magenta toner image to the transfer paper P is electrostatically collected by the cleaning roller 10 in exactly the same manner as described above with reference to FIGS. 11 to 14. The collected toner redeposits on the surface of the photoconductor, and the redeposited toner and the magenta transfer residual toner passing through the cleaning roller 10 are electrostatically collected by the developing device 4M.

After that, cyan and black toner images are formed in exactly the same manner as described above, and after these are respectively transferred to the transfer paper P, the transfer residual toner adhering to the surface of the photoconductor is as described above. In the same manner, they are finally electrostatically collected by the developing devices 4C and 4B.

Other configurations and operations of the embodiment shown in FIGS. 11 to 14 are the same as those of the embodiment described above with reference to FIGS. 1 to 10.

As described above, according to the color image forming method of this embodiment, the electrostatic latent image is formed on the image carrier composed of the photoconductor 1 in the structure of the embodiment corresponding to claim 1 described above. From the time immediately after the rear end in the circumferential direction of the image carrier of the image forming area where the electrostatic latent image is formed has passed through the cleaning member composed of the cleaning roller 10 during the formation, the rotation of the image carrier is accompanied. The toner re-adhesion operation from the cleaning member to the surface of the image carrier is started at a suitable time until the rear end of the image forming area reaches the cleaning member again, and the toner is collected by the cleaning member after the operation is started. Instead, the transfer residual toners of the respective colors on the surface of the image carrier that have passed through the cleaning member are electrostatically collected in the respective developing devices 4Y, 4M, 4C, 4B containing the developers of the respective colors. Is constructed sea urchin. This is an example of an embodiment corresponding to claim 2.

According to the above arrangement, after the toner images of the respective colors are transferred onto the transfer paper, the toners collected on the cleaning member are carried on the image carrying member before the transfer member is completely collected on the surface of the image carrying member. Since redeposition on the body surface is started, the surface of the image carrier immediately behind a certain image forming area can be changed to the next image forming area, and the image forming speed can be increased. In the example shown in FIGS. 3 to 10, all the transfer residual toner is removed by the cleaning roller 1.
Since the toner is reattached to the surface of the photoconductor after being collected to 0, a relatively large area Z for reattaching the toner is required between one image forming area and the next image forming area. Therefore, it takes a relatively long time to form a full-color image on one sheet of transfer paper P. However, in the example shown in FIGS. 11 to 14, toner is redeposited between the image forming areas. The image forming speed can be increased by that much without requiring a large area for performing the process.

Further, in the example shown in FIGS. 11 to 14, as described above, in the embodiment corresponding to the above-mentioned claim 2, the cleaning member composed of the cleaning roller 10 and the image composed of the photoreceptor 1 are formed. When the operation of re-adhering the toner to the surface of the carrier is performed, the surface of the cleaning member and the surface of the image carrier move in the same direction at the contact portions of the both, and the linear velocities of the both surfaces are different from each other. Thus, the rotation of the cleaning member is controlled. This is an example of an embodiment corresponding to claim 3. According to such a configuration, as described above, the effect of re-adhering toner to the surface of the image carrier is enhanced, and the cleaning member is not collected by the cleaning member. The transfer residual toner passing through is efficiently triboelectrically charged to a predetermined polarity, that is, the same polarity as the toner at the time of development, and electrostatically reliably collected in the developing device containing the developer of that color. be able to.

Further, in the example shown in FIGS. 11 to 14,
The rear end Y3 of the image forming area is again cleaned by the cleaning roller 1.
Before re-adhesion of the toner from the cleaning roller 10 to the photoconductor 1 is completed before reaching the position 0, the above-mentioned operation itself when re-adhering the toner from the cleaning roller 10 to the photoconductor 1 is The process is performed until the rear end 3Y of the forming area reaches the cleaning roller 10 again. That is, in the above-described embodiment corresponding to claim 3, at least the operation of reattaching the toner from the cleaning member including the cleaning roller 10 to the surface of the image bearing member including the photoconductor 1 is performed in the image forming area. The process is performed until the rear end reaches the cleaning member again. This is an example of an embodiment corresponding to claim 4,
According to this configuration, the transfer residual toner that passes through the transfer unit 8 and enters the cleaning roller 10 is a mixture of positively and negatively charged toner, but the toner is not collected by the cleaning roller 10 and passes through it. even when,
By the frictional action between the cleaning roller 10 and the photoreceptor 1, the entire transfer residual toner can be surely triboelectrically charged to the predetermined first polarity, in this example, the negative polarity, and the toner is charged with the developer of that color. It is possible to surely electrostatically collect the toner in the developing device accommodated therein, and it is possible to effectively suppress the problem that the transfer residual toner is left on the photosensitive member and the toner image formed next has a background stain.

In the example described above with reference to FIGS. 11 to 14, as shown in FIG. 11, immediately after the trailing edge Y3 of the image forming area Y1 has passed the cleaning roller 10,
The re-adhesion operation of the toner from the cleaning roller 10 to the photoconductor 1 is started. The start time of this operation is, as described above, when the electrostatic latent image is formed on the image carrier. Immediately after the rear end of the image forming area in which the electrostatic latent image is formed in the circumferential direction of the image carrier passes through the cleaning member, the rear end of the image forming area is again cleaned as the image carrier rotates. It may be timely until just before the time. If the toner is reattached to the photoconductor at this time, the toner from the cleaning member can be reattached to the surface portion of the image carrier that does not affect the formation of any toner image.

For example, the image forming area Y1 shown in FIG.
When the trailing edge Y3 passes through the exposure unit 3 and the optical writing to the image forming area is completed, and this is detected by a detection unit (not shown), based on the detection signal, the cleaning roller 10 causes the photosensitive member to move. The operation of re-adhering the toner to the first toner may be started.

Alternatively, the rear end Y of the above-mentioned image forming area Y1
3 passes through the developing device 4Y, and when the detection unit (not shown) detects that the developing device 4Y has completed the operation of forming the toner image, or the trailing edge Y3 passes through the transfer portion 8 and the toner image When the completion of transfer is detected by a detection unit (not shown), the operation of re-adhering the toner from the cleaning roller 10 to the photoconductor 1 may be started. This configuration can be similarly applied to the readhesion start timing of toners of other colors.

15 to 21 show an embodiment corresponding to claims 5 to 7. The basic configuration of the color image forming apparatus and the image forming method thereof shown in FIG. 15 is the same as that of the image forming apparatus shown in FIG. That is, also in the color image forming apparatus shown in FIG. 15, electrostatic latent images for different colors are sequentially formed on the image carrier composed of the rotationally driven photoconductor 1,
Each of the electrostatic latent images is developed by a plurality of developing devices 4 containing developer YD, MD, CD, BD of different colors.
Each of Y, 4M, 4C, and 4B sequentially visualizes toner images of different colors, and the toner images of the respective colors are sequentially printed on the same recording medium, that is, the transfer paper P wound around the transfer drum 6. When the toner images of the respective colors are transferred, the transfer residual toner adhering to the surface of the image carrier after the transfer of each toner image is electrostatically applied to the surface of the cleaning member composed of one rotating cleaning roller 10. Of each color, the collected toners are electrostatically returned to the surface of the image carrier to be re-adhered to the surface of the image carrier, and the re-adhered toners of the respective colors are stored in the developer containing the developers of the respective colors. Each of the developing devices 4Y, 4M, 4C, and 4B is configured to electrostatically collect. Therefore, FIG.
1 corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and mainly different points from the previous embodiment will be described below.

The cleaning roller 10 shown in FIG. 15 is also composed of a conductive central shaft 13 and an elastic body 14 integrally provided around the central shaft 13, and the peripheral surface thereof is the photosensitive member 1.
A region corresponding to the number of colors of the toner image formed above, that is, the first to fourth four toner recovery regions 17 in this example.
It is divided into Y, 17M, 17C and 17B. Then, the transfer residual toners on the photoconductor are electrostatically collected in the respective areas.

FIG. 16 shows a state in which the tip Y2 of the image forming area Y1 of the yellow toner image which has passed through the transfer section 8 (FIG. 15) reaches the cleaning section 15 by the cleaning roller 10. At this time, the portion 1 in the first toner collecting area 17Y on the surface of the cleaning roller 10
8Y comes into contact with the photoconductor 1, and in this state the cleaning roller 10 is rotationally driven counterclockwise at a relatively low speed, and the transfer residual toner T ₁ is fed to the central shaft 13 thereof by the power source E ₃ .
A second polarity, which is the opposite polarity to the charging polarity of, that is, a positive voltage is applied. In this way, the photoconductor 1 and the cleaning roller 10 contact each other at the contact portion between the cleaning portion 1 and the cleaning portion 1.
5, the transfer residual toner T ₁ adhering to the image forming area Y1 after the toner image is transferred is electrostatically transferred to the first toner collecting area 17Y on the surface of the cleaning roller 10. It is attracted to and collected. Also at this time, the transfer residual toner T ₁ is triboelectrically charged between the cleaning roller 10 and the photoconductor 1 to be charged to the first polarity, that is, the negative polarity, and the charging polarity is made uniform so that the cleaning roller 10 has the first polarity. The toner is collected in the first toner collecting area 17Y.

FIG. 17 shows a state in which the trailing edge Y3 of the image forming area Y1 of the yellow toner image reaches the cleaning portion 15, and at this time, the cleaning roller 10
The portion 19Y of the first toner collecting area 17Y in the above is in contact with the photoconductor 1. At this point, the transfer residual toner T ₁ attached to the image forming area Y1 after the toner image is transferred, that is, the cleaning operation of the surface of the photoconductor is completed. After the toner is collected by the cleaning roller 10 in this manner, the toner T ₂ is retained and not returned to the photoconductor 1.

Next, the cleaning roller 10 is further rotated slightly counterclockwise, and as shown in FIG. 18, the portion 18M of the second toner collecting area 17M is moved to the photosensitive member 1.
Stop the cleaning roller 10 in the state of contacting the
The positive voltage having the second polarity is continuously applied to the cleaning roller 10. On the other hand, just as in the case of the image forming apparatus shown in FIG. 1, a magenta toner image is formed on the surface of the photoconductor, and the toner image is transferred onto the transfer paper P. The cleaning roller 10 starts to rotate counterclockwise from the time when the tip M2 of the image forming area M1 of the image reaches the cleaning unit 15, and the second transfer is performed in the same manner as when the transfer residual toner of the yellow toner is collected. The transfer residual toner T ₁ of the magenta toner image is electrostatically collected in the toner collecting area 17M of the above.

FIG. 19 shows a state in which the toner collecting operation is completed, and at this time, the portion 19M of the second toner collecting area 17M is in contact with the photoconductor 1. In this case as well, the collected toner T ₂ is held on the photoreceptor 1 without being reattached.

In the same manner, the cleaning roller 10
The transfer residual toner of the cyan toner image is electrostatically collected on the third toner collecting area 17C, and the remaining toner is carried.

Subsequently, the transfer residual toner of the black toner image is electrostatically collected on the fourth toner collecting area 17B of the cleaning roller 10 in the same manner.

As described above, the toner images of the respective colors are sequentially transferred onto the same transfer paper P in an overlapping manner, and each time the toner images of the respective colors are transferred, they are attached to the surface of the image carrier after the transfer of the respective toner images. The transfer residual toner is different from each other in toner collecting regions 17Y, 17M, 17 in the circumferential direction of the surface of the cleaning member formed by one rotating cleaning roller 10.
Each of C and 17B is electrostatically recovered.

Here, all the toner images other than the black toner image finally formed on the photosensitive member, that is, the transfer residual toners adhering to the surface of the photosensitive member after the transfer of the yellow, magenta and cyan toner images are all cleaning rollers. 10
Of the toner remaining in the black toner image formed on the photoconductor, the toner remaining in the fourth toner collecting area 17B of the cleaning roller 10 is entirely collected in the toner collecting areas 17Y, 17M, and 17C. Before being collected, it is electrostatically returned to the surface of the photoreceptor as follows. This is basically the same as the operation described above with reference to FIGS. 11 to 14.

FIG. 20 shows a state immediately after the trailing edge B3 of the image forming area B1 of the black toner image finally formed on the photoconductor 1 has passed the cleaning section 15.
At this time, the charging roller 2 is attached to the image forming area B1.
Is charged, the electrostatic latent image is formed by irradiation with the laser beam L, and the electrostatic latent image is visualized by the black developing device 4B. Has been transcribed to. FIG. 20 is a diagram corresponding to FIG. 11 described above.

On the other hand, in FIG. 21, the trailing edge B3 of the image forming area B1 of the black toner image is changed by the rotation of the photoconductor 1.
A state immediately before reaching the portion of the cleaning roller 10 is shown again, and this figure corresponds to FIG. 14 described above.

Here, the black toner T ₂ collected in the fourth toner collecting area 17B of the cleaning roller 10
20 starts to be redeposited from the cleaning roller 10 to the surface of the photoconductor 1 at a proper time from the time point shown in FIG. 20 to the time point shown in FIG.

Of a plurality of toner images of different colors, the toner image formed last on the surface of the image carrier composed of the photoconductor 1, in this example, the electrostatic latent image for the black toner image is the image carrier. When the electrostatic latent image is formed on the surface of the image carrier, the rear end of the image forming region in the circumferential direction of the image carrier passes through the cleaning member including the cleaning roller 10. Then, the toner image finally formed on the surface of the image carrier is timely until just before the rear end of the image forming area reaches the cleaning member again,
That is, the operation of reattaching the toner of the color of the black toner image from the cleaning member to the surface of the image carrier is started.

Here, similarly to the example shown above with reference to FIGS. 11 to 14, the time point shown in FIG. 20 immediately after the trailing edge B3 of the image forming area B1 of the black toner image has passed through the cleaning section 15. Assuming that the black toner re-adhesion operation to the photoconductor 1 is started, the cleaning roller 10 is rotationally driven in the counterclockwise direction up to this point, and the photoconductor 1 contacts the photoconductor 1 at the contact portion. The cleaning roller 10 rotates in a direction opposite to the moving direction, and the cleaning roller 10 has a second positive polarity opposite to the charging polarity of the black transfer residual toner frictionally charged between the cleaning roller 10 and the photoconductor 1. Polarity voltage is applied.

On the other hand, in the state shown in FIG. 20,
A voltage having a first polarity, which is the same polarity as the charging polarity of the black toner collected therein, that is, a negative polarity, is applied to the cleaning roller 10 by a power source E ₄ (FIG. 15), and the cleaning roller 10 rotates in the rotation direction. The cleaning roller 10 is switched to the photosensitive member 1
At the contacting portion with and, the surface is rotationally driven in a direction in which the surface moves in the same direction as the surface of the photoconductor (see FIG. 21). As a result, the black toner T ₂ collected on the surface of the cleaning roller 10 starts to electrostatically transfer to the surface of the photoconductor 1 and re-adheres to the surface of the photoconductor 1.

The black toner redeposited on the surface of the photoconductor is electrostatically collected by the developing roller 5B when it reaches the developing device 4B as the photoconductor 1 rotates, and is reused here.

Even after the re-adhesion operation of the black toner from the cleaning roller 10 to the photosensitive member 1, the black transfer residual toner T _{1 which} has passed through the transfer portion 8 is left in the region where the cleaning roller 10 is pressed against the surface of the photosensitive member _1. Is carried while being carried on the surface of the photoconductor, the toner T ₁ is again fed to the cleaning roller 10 at the rear end B3 of the image forming area B1.
21 is reached, that is, immediately after the time point shown in FIG. In this way, the transfer residual toner T ₁ sent to the portion of the cleaning roller 10 is not collected by the cleaning roller 10 that has already started the re-adhesion operation, but passes through the cleaning roller 10.

The cleaning roller 10 rotates so as to move in the same direction as the surface of the photoconductor 1 at the contact portion with the photoconductor 1, but at this time, the cleaning roller 1
The rotation of the cleaning roller 10 is controlled so that the linear velocities of the surface 0 and the surface of the photoconductor 1 are different from each other. For example,
The rotation speed of the cleaning roller 10 is set so that the peripheral speed of the surface of the cleaning roller 10 is faster than the peripheral speed of the surface of the photoconductor 1, or vice versa. The rotation speed of the cleaning roller 10 is set so as to be slower than the linear speed of the surface. Accordingly, when the transfer residual toner T ₁ of the the photosensitive member 1 passes through the site of the cleaning roller 10, subjected to rubbing action from the photoreceptor 1 and the cleaning roller 10, whereby when the recovery of the black transfer residual toner to the cleaning roller 10 Similarly, the transfer residual toner T ₁ is triboelectrically charged to the first polarity which is the same as the charging polarity of the toner at the time of development, that is, the negative polarity, and the charging polarity is made uniform. At this time, since the cleaning roller 10 is applied with the first polarity, that is, a negative voltage, the transfer residual toner T ₁ having a negative charging polarity is collected by the cleaning roller 10 without being collected. pass. When the toner thus charged to the negative polarity reaches the developing device 4B, it is efficiently electrostatically collected by the developing roller 5B to which the voltage of the positive polarity is applied, and the photosensitive member after passing through the developing device 4B is exposed. The body surface is cleaned.
In this way, when the photoconductor 1 further rotates counterclockwise from the state of FIG. 21 and the rear end B3 of the image forming area B1 passes the developing device 4B again, the image forming area B1
All of the transfer residual toner above has been collected by the developing device 4B,
The cleaning of the surface is completed.

Immediately after the time point shown in FIG. 21, the trailing edge B3 of the image forming area B1 passes through the portion of the cleaning roller 10, and at this time, the fourth edge of the cleaning roller 10 is reached.
The operation for reattaching the toner from the toner collecting area 17B to the surface of the photoconductor 1 is completed.

As described above, even after the trailing edge B3 of the image forming area B1 of the toner image finally formed on the photoconductor 1 has passed through the cleaning member composed of the cleaning roller 10, the cleaning member is still While the polarity of 1, that is, the negative voltage is continuously applied, the cleaning member is rotationally driven in the clockwise direction, and the other colors, that is, cyan and magenta, collected in the toner collecting regions 17C, 17M, and 17Y of the cleaning member, respectively. And yellow toner T ₂ are sequentially and separately reattached to the surface of the image carrier, and the respective reattached toners are developed by the developing devices 4C, 4M, 4Y.
Developing rollers 5 to which a second positive polarity voltage of
C, 5M, 5Y are sequentially electrostatically recovered. The toner of each color redeposited on the surface of the image carrier and the toner remaining after the transfer of the toner image formed last on the surface of the image carrier, which has passed through the cleaning member without being collected by the cleaning member, The developer of each color is electrostatically collected in each developing device.

It is necessary to collect the toner in the developing device separately for each color toner. In this example, first, the developing device 4 is used.
A positive voltage is applied to the B developing roller 5B, whereby the black toner is collected by the developing roller 5B. At this time, the other developing devices are deactivated, a positive voltage is not applied to the developing rollers 5Y, 5M, 5C, and the black toner is not collected by the other developing devices 4Y, 4M, 4C. Similarly, when the cyan redeposited toner is collected by the developing device 4C, a positive voltage is applied only to the developing roller 5C, and when the magenta redeposited toner is collected by the developing device 4M, the developing roller 4C is collected. When recovering the redeposited toner of 5 M only to the developing roller 4Y, the positive polarity voltage is applied only to the developing roller 5Y. The redeposited toners of different colors on the surface of the photoconductor are carried and conveyed while being separated from each other in the circumferential direction of the photoconductor. In this way, color mixing of toners of different colors is prevented.

The configuration described above with reference to FIGS. 15 to 21 is an embodiment corresponding to claim 5. According to this configuration, using only one cleaning member,
The transfer residual toner of each color on the surface of the photoconductor is collected by the cleaning roller 10, and then the collected toner is reattached to the surface of the photoconductor, and these can be collected by a predetermined developing device.

Further, the toner is collected in the toner collecting areas 17Y, 17M, 17C and 17B of the cleaning roller 10, and the collected toners are held once. Therefore, when the collected toners are re-attached to the photoconductor 1, It is not necessary to reattach the toner to the non-image forming areas behind the image forming areas on the photoconductor. Therefore, the non-image forming area between the image forming areas can be made extremely small or can be eliminated. Moreover, the re-adhesion operation of each toner can be performed when the transfer paper P is separated from the transfer drum 6, and it is possible to effectively prevent the image forming speed from being lowered by the re-adhesion operation.

Further, as in the case of the embodiment shown in FIG. 11 to FIG. 14, before all the transfer residual toner of the black toner image finally formed on the photoconductor 1 is collected by the cleaning roller 10, Since the black toner collected on the cleaning roller 10 starts to be reattached to the surface of the photoconductor 1, the image forming speed can also be improved by this.

Further, also in the embodiment examples shown in FIGS. 15 to 21, as in the examples shown in FIGS. 11 to 14,
The redeposition operation of the black toner to the photoconductor 1 may be started at the time shown in FIG. 20, or the redeposition operation may be started at another appropriate time. For example, the trailing edge B3 of the image forming area B1 for the black toner image
Passes through the exposure unit 3 (FIG. 15) to complete the optical writing on the photoconductor 1, or the trailing edge B3 passes through the developing device 4B to finish the formation of the black toner image, or the trailing edge B3. When the black toner image has passed through the transfer portion 8 and has finished transferring the black toner image, either one of them is detected by a detection unit (not shown), whereby the cleaning roller 1 is detected.
The redeposition operation of the black toner from 0 to the photoconductor 1 may be started.

The embodiment shown in FIGS. 15 to 21 is the same as the embodiment corresponding to claim 5 described above.
When performing the operation of re-adhering the toner of the color of the toner image finally formed on the surface of the image carrier composed of the photoconductor 1 from the cleaning member composed of the cleaning roller 10 to the surface of the image carrier, the cleaning member. The rotation of the cleaning member is controlled so that the surface and the surface of the image carrier move in the same direction at the contact portions of the both and the linear velocities of the both surfaces are different from each other. This is an example of an embodiment corresponding to claim 6, but according to such a configuration, the effect of re-adhesion of the toner to the surface of the image bearing member is enhanced, and the toner passing through this without being collected by the cleaning member is predetermined. It is possible to surely perform triboelectrification to the first polarity and surely electrostatically collect this in the developing device containing the developer of that color.

Further, in the example shown in FIGS. 15 to 21, before the rear end B3 of the image forming area B1 reaches the portion of the cleaning roller 10 again, the cleaning roller 10
Even when the re-adhesion of the black toner to the photosensitive member 1 is completed, it is desirable that the re-adhesion operation of the toner by the cleaning roller 10 itself is executed until the rear end B3 reaches the portion of the cleaning roller 10 again. . That is, in the example of the embodiment corresponding to claim 6 described above, the toner image finally formed on the surface of the image carrier composed of the photoconductor 1, that is, the toner of the color of the black toner image, is cleaned by the cleaning roller 10. The operation of reattaching the toner image to the surface of the image carrier is performed at least until the trailing edge of the image forming area of the toner image finally formed reaches the cleaning member again. This is an example of an embodiment corresponding to claim 7, and by such a configuration, all of the transfer residual toner that passes through the cleaning roller 10 without being collected is frictionally charged to the first negative polarity, and this is changed to that of that color. It is possible to surely electrostatically collect the developer in the developing device containing the developer.

In the examples shown in FIGS. 15 to 21,
Each toner recovery area 17Y, 1 of the cleaning roller 10
The collected toner is not attached to the entire surface of 7M, 17C, and 17B, and the central area (in the case of the first area 17Y, the part 1
The collected toner was adhered only to the area from 8Y to the portion 19Y. This is because if the collected toner is attached even to the boundary between the respective toner collecting areas, the toners of different colors may be mixed with each other to cause color mixing. When there is no risk of such color mixing, or when the degree thereof is extremely slight, each toner recovery area 17 of the cleaning roller 10
The collected toner may be attached to the entire surface of Y, 17M, 17C and 17B.

By the way, as described above, in the charging roller 2 shown in FIGS. 1 and 15, the re-adhered toner on the photoconductor 1 can pass through this charging roller 2 portion.
It is separated from the surface of the photoconductor 1. Further, it is preferable to keep the charging roller 2 away from the photoconductor 1 even when the operation of the image forming apparatus is stopped. When the charging roller 2 is constantly in contact with the surface of the photoconductor, for example, the vulcanizing agent mixed in the charging roller 2 oozes out onto the surface of the photoconductor 1, which causes poor charging and poor development of the photoconductor. However, problems such as streaks in the toner image may occur.

For this reason, the charging roller 2 of this example is supported so as to be able to come into contact with and separate from the surface of the photoconductor 1, and a configuration example relating to the contact and separation will be described below.

In FIG. 22, each end of the roller shaft of the charging roller 2 is rotatably supported by bearings 47, 48, and each bearing 47, 48 is an elongated hole formed in each supporting member 45, 46. Is slidably fitted to the charging roller 2, and the charging roller 2 is biased by a spring 49 (only one of which is shown) in a direction in which the charging roller 2 is pressed against the surface of the photoconductor 1 shown in FIGS.
Both supporting members 45, 46 are fixed at their base end portions to a supporting shaft 44 extending parallel to the photosensitive member.
Reference numeral 4 is rotatably supported by a frame (not shown) of the image forming apparatus main body. A base end portion of an arm 50 is fixed to one end portion of the support shaft 44, and a link 51 connected to a plunger of a solenoid 52 is pivotally attached to the tip end side of the arm 50.

When the solenoid 52 is turned off, the link 5
1 is biased in the direction of the arrow, at which time the charging roller 2 is separated from the surface of the photoconductor.

When the print button of the image forming apparatus is pressed, the solenoid 52 is turned on, which causes the link 5
1 is pulled in the direction opposite to the arrow, which causes the arm 50
And the support shaft 44 rotates clockwise in the drawing. Therefore, the charging roller 2 contacts the surface of the photoconductor. At this time, the charging roller 2 is pressed against the surface of the photoconductor while being pressed by the pair of springs 49.

When the charging operation of the predetermined image forming area with respect to the photosensitive member 1 is completed, the solenoid 52 is turned off, whereby the charging roller 2 is separated from the surface of the photosensitive member, and the next image forming area is located on the charging roller 2 portion. Immediately before reaching, the solenoid 52 is again urged to press the charging roller 2 against the surface of the photoconductor. In this way, the charging roller 2 comes into contact with and separates from the photoconductor.

The present invention is widely applicable to a color image forming method using an endless belt as a cleaning member, a color image forming method using an endless belt as an image carrier, and the like.

An intermediate transfer member is used as a recording medium,
It can also be applied to a color image forming method of a type in which toner images of respective colors are sequentially transferred from an image carrier to the intermediate transfer member and then transferred to a final recording medium such as transfer paper.

Further, according to the present invention, after the image bearing member is charged by the charging device, an electrostatic latent image is formed by a portion which is not irradiated with light when the surface of the image bearing member is exposed to an image, and the latent image charge has the opposite polarity. It can also be applied to a so-called positive / positive developing type image forming method in which a toner charged to a polarity is attached to the electrostatic latent image to perform development.

Further, instead of using a plurality of developing devices juxtaposed on the image carrier, a plurality of developing devices are assembled into a rotating body, and each developing device faces the image carrier by the rotation of the rotating body. The present invention can be applied without any problems to a color image forming method in which the electrostatic latent image is visualized by bringing it to the developing position.

[0140]

According to the color image forming method of the present invention, by using only one cleaning member, the transfer residual toner of each color on the surface of the image carrier is collected by the cleaning member, and then the cleaning member is collected. The toner can be reattached to the surface of the image bearing member, and each reattached toner can be collected in a predetermined developing device, and the toner can be effectively recycled and used with a simple configuration. In addition, since toners of different colors are not collected at the same time by the cleaning member, it is possible to prevent toner color mixture on the cleaning member.

According to the color image forming method of the second aspect, in addition to the above-described function and effect, the effect that the image forming speed can be increased can be obtained.

According to the color image forming method of the third aspect, the re-adhesion of the toner from the cleaning member to the surface of the image bearing member can be efficiently performed, and the transfer residue passing through the cleaning member without being recovered. It is possible to efficiently triboelectrically charge the toner to a predetermined polarity and reliably collect the toner in a predetermined developing device.

According to the color image forming apparatus of the fourth aspect, the entire transfer residual toner, which passes through the cleaning member without being collected, is efficiently triboelectrically charged to a predetermined polarity, and is securely transferred to a predetermined developing device. Can be collected.

According to the color image forming method of the fifth aspect, the transfer residual toner of each color on the surface of the image bearing member is collected by the cleaning member by using only one cleaning member, and then the collected toner is collected. The toner can be reattached to the surface of the image carrier, and the respective reattached toners can be collected in a predetermined developing device, and the toner can be effectively recycled and used with a simple structure, and the image forming speed can be increased.

According to the color image forming method of the sixth aspect, in addition to the above-described function and effect, the toner can be efficiently reattached from the cleaning member to the surface of the image bearing member, and the toner can be collected in the cleaning member. It is possible to efficiently triboelectrically transfer untransferred toner to a predetermined polarity and to collect the transfer residual toner in a predetermined developing device.

According to the color image forming method of the seventh aspect, the entire transfer residual toner, which passes through the cleaning member without being collected, is efficiently triboelectrically charged to a predetermined polarity, and is securely transferred to a predetermined developing device. Can be collected.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional schematic explanatory view showing an example of a color image forming apparatus.

FIG. 2 is an explanatory diagram schematically showing a frictional contact portion of both of the photosensitive member and the cleaning roller and the toner in order to explain that the charging polarities of the toner are made uniform.

FIG. 3 is an explanatory diagram showing a state in which the transfer residual toner on the photoconductor is being collected by a cleaning roller.

FIG. 4 is an explanatory diagram showing a state when a rear end of an image forming area reaches a portion facing a charging roller.

FIG. 5 is an explanatory diagram showing a state when the rear end of the image forming area reaches a portion facing the developing roller.

FIG. 6 is an explanatory diagram showing a state when the rear end of the image forming area reaches a portion facing the cleaning roller.

FIG. 7 is an explanatory diagram showing a state where toner collected on a cleaning roller is reattached to a photoconductor.

FIG. 8 is an explanatory diagram showing a state in which redeposited toner on a photoconductor is conveyed toward a developing device.

FIG. 9 is an explanatory diagram showing a state in which redeposited toner on a photoconductor is collected by a developing device.

FIG. 10 is an explanatory diagram showing a state when the leading edge of the image forming area for the next magenta toner image reaches the transfer portion.

FIG. 11 is an explanatory diagram showing a state immediately after the rear end of the image forming area has passed the cleaning roller.

FIG. 12 is an explanatory diagram showing a state where the rear end of the image forming area shown in FIG. 11 has reached the portion of the charging roller.

FIG. 13 is an explanatory diagram showing a state when the rear end of the developing roller has passed a developing roller.

FIG. 14 is an explanatory diagram showing a state immediately before the rear end reaches the portion of the cleaning roller again.

FIG. 15 is a partial cross-sectional schematic explanatory view showing a color image forming apparatus which is partially different from FIG.

FIG. 16 is an explanatory diagram showing a state when the transfer residual toner is started to be collected in the first toner collecting area of the cleaning roller.

FIG. 17 is an explanatory diagram showing a state when the transfer residual toner is completely collected in the first toner collecting area.

FIG. 18 is an explanatory diagram showing a state when the transfer residual toner is started to be collected in the second toner collecting area of the cleaning roller.

FIG. 19 is an explanatory diagram showing a state when the transfer residual toner is completely collected in the second toner collecting area.

FIG. 20 is an explanatory diagram showing a state immediately after the rear end of the image forming area has passed the cleaning roller.

FIG. 21 is an explanatory diagram showing a state immediately before the rear end of the image forming area shown in FIG. 20 reaches the portion of the cleaning roller again.

FIG. 22 is a perspective view showing an example of a contacting / separating unit for contacting / separating the charging roller with respect to the surface of the photosensitive member.

[Explanation of symbols]

4Y developing device 4M developing device 4C developing device 4B developing device 17Y toner collecting area 17M toner collecting area 17C toner collecting area 17B toner collecting area YD developer MD developer CD developer BD developer T ₁ toner T ₂ toner T ₃ toner

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-152832 (JP, A) JP-A-8-328440 (JP, A) JP-A-1-161287 (JP, A) JP-A-9- 236962 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 21/00 G03G 21/10-21/12 G03G 15/01-15/01 117 G03G 15/00 303 G03G 21 / 00 370-540 G03G 21/14 G03G 15/08-15/08 507

Claims (7)

(57) [Claims] 1. An electrostatic latent image for different colors is sequentially formed on a rotationally driven image carrier, and each electrostatic latent image is developed by a plurality of developing agents containing developers of different colors. The toner images of different colors are sequentially visualized by the respective devices, and the toner images of the respective colors are sequentially superimposed and transferred onto the same recording medium, and the toner images of the respective toner images are transferred for each transfer. The transfer residual toner adhering to the surface of the image bearing member after the image transfer is electrostatically collected by one rotating cleaning member to clean the surface of the image bearing member, and the cleaning member is cleaned after each toner collecting operation. The toner collected in step (1) is electrostatically redeposited on the surface portion of the image carrier that does not affect the formation of the next toner image on the surface of the image carrier, and the toner of each color redeposited on the surface of the image carrier is attached. , Containing the developer of each color A color image forming method in which each developing device electrostatically collects. 2. When an electrostatic latent image is formed on the image carrier, from immediately after the rear end in the circumferential direction of the image carrier of the image forming area where the electrostatic latent image is formed has passed through the cleaning member. In accordance with the rotation of the image carrier, the re-adhesion operation of the toner from the cleaning member to the surface of the image carrier is started in a timely manner immediately before the rear end of the image forming area reaches the cleaning member again. After the operation is started, the transfer residual toner of each color on the surface of the image carrier that has not passed through the cleaning member and is not recovered by the cleaning member is electrostatically recovered in each developing device containing the developer of each color. Item 2. The color image forming method according to Item 1. 3. When the operation of reattaching the toner from the cleaning member to the surface of the image bearing member is performed, the surface of the cleaning member and the surface of the image bearing member move in the same direction at their contact portions, and The color image forming method according to claim 2, wherein the rotation of the cleaning member is controlled so that the linear velocities of both surfaces are different from each other. 4. The color image formation according to claim 3, wherein the operation of reattaching the toner from the cleaning member to the surface of the image carrier is performed at least until the rear end of the image forming area reaches the cleaning member again. Method. 5. A plurality of developing devices in which electrostatic latent images for different colors are sequentially formed on a rotationally driven image carrier, and the electrostatic latent images are respectively stored in developers of different colors. The toner images of different colors are sequentially visualized by the respective devices, and the toner images of the respective colors are sequentially superimposed and transferred onto the same recording medium, and the toner images of the respective toner images are transferred for each transfer. The transfer residual toner adhering to the surface of the image bearing member after the image transfer is electrostatically collected in different toner collecting regions in the circumferential direction of one rotating cleaning member surface, and the plurality of toners having different colors from each other are collected. Of the toner images of, when the electrostatic latent image for the toner image formed last on the surface of the image carrier is formed on the image carrier,
From the time immediately after the rear end in the circumferential direction of the image carrier of the image forming area where the electrostatic latent image is formed has passed the cleaning member,
With the rotation of the image bearing member, the toner of the color of the toner image finally formed on the surface of the image bearing member is cleaned at a proper time until just before the rear end of the image forming area reaches the cleaning member again. Then, the operation of re-adhering to the surface of the image carrier is started, and after the trailing edge of the image forming area again passes through the cleaning member, the toners of other colors collected by the cleaning member are sequentially and separately applied to the surface of the image carrier. The toner of each color that has been reattached and redeposited on the surface of the image carrier, and the transfer residual toner of the toner image formed last on the surface of the image carrier, have passed through the cleaning member without being collected by the cleaning member. A color image forming method in which toner is electrostatically collected in each developing device containing a developer of each color. 6. The surface of the cleaning member and the surface of the image carrier when the operation of reattaching the toner of the color of the toner image finally formed on the surface of the image carrier from the cleaning member to the surface of the image carrier. 6. The rotation of the cleaning member is controlled so that the contact portions of both of them move in the same direction and the linear velocities of both surfaces are different from each other.
The method for forming a color image according to item 1. 7. An operation of re-adhering the toner of the color of the toner image formed last on the surface of the image carrier from the cleaning member to the surface of the image carrier at least the image formation of the toner image formed last. The color image forming method according to claim 6, wherein the process is performed until the rear end of the area reaches the cleaning member again.